Numerous species of biological agents, including, but not limited to, protozoans parasites, bacteria, fungi, or viruses enter water systems or enter the atmosphere from sources such as solid waste material, commercial processing wastes, sewage effluent, septic tanks effluents, sewage sludge, garbage disposal, urban runoff, medical facilities, agricultural runoff, human beings sneezing or coughing and the like.
Bacteria are well adapted to and are common biological agents in water systems. Bacteria may have ranges in size from about 1000 nanometers (nm) to about 10,000 nm in size and include species such as Aeromonas, campylobacter, Escherichia coli, Helicobacter pylori, Legionella, Nontuberculosis mycobacteria, Psedomonas aeruginosa, salmonella, shigella, Vibrio vholerae, Yersinia enterocolitica, and the like bacteria.
Major bacteria identified in ambient air include species such as: Acinetobacter, Ordetella perfussis, Corynebacteria diphtheria, Mycobacterium avium, Pseudomonas aeruginosa, Staphylococcus aureus, and the like bacteria.
Viruses have been detected in all environments including water systems as described by Gerba, C. P. and Rose, J. B., “Viruses in Source and Drinking Water”, Drinking Water Microbiology (1990), incorporated by reference herein, and in ambient air. Most viruses are small (about 20 nm to about 200 nm) and consist of nucleic acid encapsulated in protein molecules. In municipal sewage, more than 100 different viruses may be identified, and viruses such as poliovirus, hepatitis A, echo, coxsackie, rota, adeno, or Norwalk-like viruses are virulently hazardous at very low concentrations. In ambient air, viruses such as adenovirus, coronavirus, echovirus, influenza, and rhinovirus have been widely detected.
Because the occurrence of pathogenic biological agents in water and air systems constitutes a serious threat to human health and can be the source of a variety of diseases, such as gastroenteritis, cholera, hepatitis, typhoid fever, giardiasis, or the like, the United States Environmental Protection Agency is in the process of addressing the public health risk resulting from pathogenic contamination of water systems.
However, the use of conventional large-scale water purification technologies such as ultraviolet irradiation or chlorination may allow concentrations of pathogenic biological agents to survive. As such, secondary treatment of conventionally treated water may be necessary to completely capture or remove biological agents in water systems. In addition, these technologies are largely not available in rural areas, military operations, tourism sites, etc. Under such circumstances, portable apparatus with low or no power requirements are in need to remove bioagents from the water systems.
To meet the demand for secondary treatment technology, including, but not limited to, commercial or residential secondary water treatment, a variety of distillation, reverse osmosis, and filtration systems have been developed which utilize evaporation, activated carbon, ion exchange resins, or reverse osmosis membranes to further purify water. However, even though these conventional technologies can be effective in the removal of certain organic compounds, and certain metals, such as lead and mercury, a variety of problems remain yet to be addressed with respect to both primary and secondary treatment methods.
A significant problem with conventional water treatment technology can be that loading capacity of activated carbon or ion exchange resins, or the like, can be low requiring frequent changes or requiring the frequent use of reactivation procedures to maintain water quality. Similarly, reverse osmosis membranes may not be suitable for purification of water with high levels of dissolved solids because the reverse osmosis membrane can become saturated or clogged with solids resulting in reduced efficiency.
Another significant problem with conventional water treatment technology can be that the amount of water processed may be low. Conventional evaporation technology and reverse osmosis technology are typically suitable only for those applications in which small volumes of water are to be purified, such as in the residential setting to purify drinking water. In addition, the energy and pressurizing requirements of reverse osmosis treatment further limit its use.
Another significant problem with conventional water treatment technology can be that sorbent materials used in conventional water treatment may possess a neutral or negatively charged surface. While some biological agents may nonspecifically interact with neutral or negatively charged sorbents, the low binding efficiency excludes the use of these sorbents to attract, capture, collect, or remove biological-agents from water systems.
These problems with conventional water treatment technology coupled with the increasing concerns over pathogenic microbial contamination of drinking water, and especially in view of recent concerns over the use of biological agents as weapons, warrant the imminent development of a cost-effective water treatment technology that can be readily applied to remove biological agents from water systems.
Moreover significant problems remain unresolved with regard to conventional air or gas treatment technology. Prominent among these problems may be that conventional gas filtration systems may only remove relatively large particulates such as pollen while allowing pathogenic agents such as viruses to pass through without retention to the filter material.
The instant invention addresses each of these concerns with respect to attracting, capturing, inactivating, or removing metal ions, inorganic and organic compounds, or biological agents from aqueous systems or gas systems whether the treatment is primary or secondary.
On the basis of their structure and properties, specific applications for layered double hydroxide (LDH) compounds and compositions have been previously identified. These include the use of LDH compounds as catalysts and catalyst precursors, as antacids, as solid ionic conductors, in preparation of pigments, to interact with anionic contaminants such as Cr2O72−, trichlorophenol (TCP), and to interact with radioactive anionic pollutants TcO4−, ReO4− and I−.